The present invention relates to a process and an apparatus for preparing a beverage under controlled pressure. More particularly, this invention relates to beverage systems using preparation chambers containing minced, ground or soluble products for the preparation of hot beverages such as coffee, tea, herbal remedies or the like in dispensing machines.
Beverage dispensing machines are widely known and used. These machines are divided into two main groups: a first group make use of disposable containers of edible products, called pods, cartridges or cartridges, that contain the ground, leaf or soluble product to be brewed or dissolved into hot water. The cartridges are disposed after having being used. The second group machines make use of a brewing chamber, usually comprising one or two pistons, where the coffee powder (or other starting material) is brewed. The remaining material is disposed after the infusion or brewing step.
There has been a constant search for a better extraction/solubilization step and for a better and constant quality of the obtained beverage.
A known method to try to improve extraction by infusion is to carry out a wetting of the coffee or other material to be extracted before the actual extraction step with pressurized hot water. This is disclosed e.g. in EP0870457, where a flexible water impermeable pod (sachet) is positioned in a chamber provided with fixed pointed means suitable to perforate the pod material once this is pressurized and biased against the chamber walls and the perforating means. According to this document, water is fed to the pod and the flow of water is interrupted before reaching a pressure sufficient to cause the perforation of the pod walls: in other words, the flow of water to the pod is stopped before it is pressurized.
WO02/076270 in the name of Tuttoespresso describes a unit system for the preparation of a beverage from a soluble product contained in a disposable cartridge that is comprising a collecting device with a housing means designed to contain the cartridge, wherein at least one throttling arrangement is provided along the flow of the beverage leaving the cartridge.
In WO04/030500, in the name of Tuttoespresso, the outlet is closed by using a perforating rod that has a diameter similar or greater than the diameter of the outlet opening in order to keep the outlet opening substantially closed during the hot water feeding step.
Closed cartridges that open upon reaching a sufficient pressure are also well known in the art.
U.S. Pat. No. 5,242,702 in the name of Nestec discloses a plastic cartridge wherein the bottom is broken open by the pressure build-up that occurs upon feeding hot water to the cartridge, with the help of a puncturing means that opens the bottom of the cartridge towards the inside.
WO2005080223, in the name of Tuttoespresso, discloses a single serve cartridge having an outlet lid portion located on a dispensing wall to form a dispensing opening after a liquid has been introduced into the cartridge, that breaks open upon pressurizing the cartridge with hot water. According to this embodiment, the outlet has portions opening towards the outside of the cartridge to let out the beverage.
EP-A-1595817 in the name of ITACA relates to a method wherein a special knurled-surface cartridge is pressurized by feeding hot water and “the pressurization of the water and of the inside of the cartridge is maintained until the breakable portions break because of the pressure”.
EP-A-1364605, in the name of Sagliaschi et al. discloses a method of preparing a beverage in a hard plastic cartridge that can resist deformation when pressurized by feeding hot water under pressure to said cartridge. Feeding of hot water is continued for an amount of time depending on the type of beverage and controlled by a timer. Eventually a piercing element perforates the bottom of the pressurized cartridge to release the beverage. In order to withstand the increasing pressure, the cartridge is made of hard rigid plastic with a thickness “calculated to make sure that the container has the necessary rigidity to withstand high pressure for long periods of time” (see para. 0034). Moreover, the cartridge has to be housed within a “watertight container” (para. 0057) to avoid the cartridge being deformed by the increasing pressure in the pressurization step.
The above methods, therefore, require that hot water is fed to the cartridge and that this pressurizing step is continued at least until an outlet is produced. During the time that is required between the start of the water feeding step and the breaking or piercing of the bottom or the forming of the opening, the coffee powder is extracted or dissolved.
These methods have several drawbacks.
The main problem with these methods is that the infusion or brewing time is depending on the pressure of the water within the cartridge, on the characteristics of the cartridge material, its manufacturing method and on the design of the cartridge outlet opening. The infusion/brewing time is therefore a variable rather than a constant; e.g. it was found that even minor changes in the cartridge material composition or in the pump efficiency or in the cartridge design would result in a different outcome of the beverage characteristics.
Therefore, the efficiency of the brewing and extraction step is also a variable and random feature of the beverage preparation.
This is true also in the case of above discussed EP-A-1364605, because a thinner area of the bottom of the cartridge is required to form the outlet opening, this thinner area being subject to possible early opening.
In order to overcome this problem it was proposed to control the flow rate of the beverage from the brewing/infusion chamber. Such a method is disclosed e.g. in US-B-6382083, wherein a valve body is positioned at the outlet of a brewing chamber, and in EP application 04031014.6 wherein several parameters are varied to control the flow rate of the beverage from the infusion/brewing chamber. Still, these methods have not completely solved the above mentioned problem, the remaining variable parameters jeopardizing the reliability of the overall results.
Still another problem is to improve the extraction of materials that have a granulometry relatively high, such as e.g ground coffee for the so-called “american” or “regular” coffee or camomile and other herbal remedies. In fact, for these types of materials it is not possible to use high extraction pressures, as are used for the espresso coffee, where the finely ground coffee particles provide a resistance sufficient to increase the dispensing pressure to 8-9 bar.
Therefore, there is the need for an improved process and apparatus for preparing and dispensing beverages, particularly hot beverages, in an easy, reliable, cost-effective way. There is also the need to improve the existing processes without having to re-design the existing cartridges and apparatuses. There is also the need to make extraction processes less dependent on the nature of the material to be extracted by brewing.